(A) Field of the Invention
The present invention relates to an over-current and over-voltage protection apparatus, and more particularly to an over-current and over-voltage protection assembly apparatus.
(B) Description of the Related Art
Telecommunications systems have become indispensable in modern daily life, as signal transmissions of telephone, networks, and other wireless communications rely heavily on telecommunications systems. Generally, conductors such as metals are used in telecommunications systems for transmitting signals, so systems may be damaged by lightning strikes. In addition to high current, lightning strikes often generate high voltages that are so damaging to telecommunication systems. Therefore, any protection apparatus applied to telecommunication systems must have both over-current protection (OCP) and over-voltage protection (OVP) characteristics.
Voltage resistances of conventional positive temperature coefficient (PTC) devices are quite sensitive to variations in temperature. When the PTC device operates in a normal state, the resistance remains extremely low, such that the circuit operates normally. However, when over-current or over-temperature occurs, the temperature rise to a threshold value causes an instant change to a high-resistance state (e.g., over 104 ohm), so as to offset the over-current. Thus, the objective to protect batteries or circuit devices can be achieved.
Generally, PTC devices can be classified into two categories, namely, polymeric PTC (PPTC) and ceramic PTC (CPTC). The PPTC and CPTC both have superior high-current resistance, and are often used as OCP devices.
In addition, varistors and gas discharge tubes are normally in a high-resistance state. When an over-voltage occurs, the varistors or gas discharge tubes will change to a low-resistance state instantly, such that the voltage is grounded. Varistors and gas discharge tubes can withstand high voltages, and thus are often used as OVP devices.
Protection apparatus of telecommunications devices are mainly implemented by integrating OCP and OVP devices. Conventionally, the OCP and OVP devices are independent devices, and must be connected with a plurality of hardware devices and covered by plastic members for fixing and insulating protection. In addition, an LED can be serially connected for indicating signal output in abnormal states, such as an over-current or an over-voltage. Though the protection apparatus manufactured with the conventional method is simple in structure and low in cost, the protection apparatus requires much time to assemble, and the volume is too large. Therefore, the conventional protection apparatus is not suitable for electronic devices that are miniaturized.
Moreover, current OCP and OVP devices also can be analog power ICs fabricated by semiconductor techniques. However, the process is complicated, and the cost is very high; thus these are not suitable for general consumer electronic product applications.